You'll have to excuse me, I am just getting in the okay zone with HTML and hoping soon to dive into style sheets

I'm attempting to create a time to count down to a certain date/time. I've visted many sites with code generators and such but I wish to know how to do it through HTML. I'm aware that the colors and look will be adjusted in the style sheet (unless I'm wrong, please correct me if this is so) but I would like to set up the code for just a basic count down.